Certificate: export from Firefox, import to Windows store

I had the same problem. Here's how I fixed it:

Go to https://www.digicert.com/util/ Download the DigiCert SSL Utility. I don't think it matters where you got the original certificate from.

Use that utility to import (upper left corner) the certificate to the Windows Store.

Bonus: I had a problem where the exporting the certificate from Windows would not import into Visual Studio. Make sure to uncheck the "Include all certificates in the certification path if possible". Visual Studio would give an error of "Cannot find the certificate and private key for decryption"

Turns out the "problem" was Firefox version: I had 59 (64 bit) while the last "working" is 57. I'm guessing 58 and later versions use a new encryption type, but didn't research to confirm.

I had to do the following:

• Export (backup) certificate from 59
• Open 57, import certificate into 57
• Export certificate from 57
• (Everything also worked on government institutions sites as well)
• Import certificate into windows certificate store (the one exported from 57)
• Uninstall 57 (or use that one for government institutions)

I found another solution using OpenSSL, which I already had installed. The trick was to convert to a .pem file only outputting client certificates, and then back to a .p12 file.

openssl pkcs12 -clcerts -in certificate.p12 -out certificate.pem
openssl pkcs12 -in certificate.pem -out certificate_win.p12

The answer by Robert about removing certificates in the certification path got me looking in the right direction, along with this page: https://blog.pki.dfn.de/2018/03/firefox-59-windows-und-probleme-mit-dem-zertifikatexport/